## find flux from a divergence

Suppose $\vec{G}$ is a vector field with the property that $div\vec{G} = 5 for 2 \leq ||\vec{r}|| \leq 14$ and that the flux of $\vec{G}$ through the sphere of radius 4 centered at the origin is $20\pi$. Find the flux of through the sphere of radius 12 centered at the origin.

I am really confused on where to start at this point